Regenerative apparatus



July 17, 1962 R. HASCHE REGENERATIVE APPARATUS Filed Feb. 27, 1958INVENTOR RudolplaLHwscZze ATTORNEYS United States PatentO" REGENERATIVEAPPARATUS Rudolph L. Hasche, Johnson City, Tenn.; Blanche K. Hasche,executrix of said Rudolph L. Hasche, deceased, assignor to CarbonicDevelopment Corporation, Johnson City, Tenn, a corporation of DelawareFiled Feb. 27, 1958, Ser. No. 717,990

7 Claims. (Cl. 23-277) This invention relates to gas reactions and moreparticularly to novel regenerative apparatus and processes whereby acombination of'endothermic and exothermic gas reactions may be elfectedat high thermal efficiency. A primary object of the invention is theprovision of a continuous method for the production of low densityheating gases, acetylene, olefins, aromatics and other endothermic gasreaction products by the partial combustion of exothermicallycombustible starting materials such as hydrocarbons and ammonia. I

Methods known to the prior art for the production of endothermicreaction products and heating gases of the aforementioned type arethermodynamically inefiicient and of restricted commercial feasibility.Conventional prior art processes entail the use of regenerative furnacesin conjunction with intermittent heating and production cycles withattendant interruptions of heating gas production. process involve thecontinuous relocation of heating zones Within a regenerative mass aswell as frequent interruptions in gas production necessitated by thecooling and required reheating of the refractory. Other conventionalpractices require long heating periods for the hydrocarbon startingmaterials and yield an inferior product containing predominantly carbonmonoxide, carbon dioxide and hydrogen. t i

It has now been discovered that low density heating gases, unsaturatedhydrocarbons including acetylene and other endothermic gas reactionproducts may continuously and substantially isothermally be produced byheating a nonllammable first mixture of an exothermically combustiblematerial and oxygen to effect incipient endothermic thermal alterationof the combustible material, thereby producing a flammable secondmixture, the so initiated endothermic reaction being propagated by theresulting exothermic combustion reaction, said combustion reaction beingcontrolled by the limited amount of oxygen present; and thereafterrapidly cooling the product so obtained, the heat resulting from saidcooling being employed to raise additional quantities of combustible ma-7 terial and oxygen to incipient cracking temperature.

For example, in thoseinstances where a hydrocarbon is employed as astarting material for the production of a heating gas, acetylene, or thelike, the hydrocarbon is first mixedin nonflamrnable proportions withair or other oxygen containing gas, and the mixture heated to theincipient thermal cracking temperature of the hydrocarbon. There isproduced in this manner a flammable second mixture containing carbon andhydrogen in addition to the hydrocarbon starting material. Thecombustion of this carbon and hydrogen together with a minor portion ofthe original hydrocarbon provides the heat required to propagate theendothermic cracking reaction. Heat released by the quenching of theproduct so obtained is utilized to heat additional quantities of thestarting mixture to the incipient cracking temperature of thehydrocarbon.

It will be appreciated that only a relatively small portion of thehydrocarbon or other combustible starting material, normally not morethan about 15% to about 40% thereof, will be consumed by the limitedcombustion reaction. The balance of the starting material will beModifications of this conventional regenerative 7 3,044,861 PatentedJuly 17,1 1962 ICC efficiently cracked or otherwise thermally altered bythe heat released by such combustion. The sensible heat of the entiregas mixture will accordingly be raised to the flame temperature of thecombustion reaction which is above that necessary to initiatethermalalteration of the starting material. Hence additional quantities ofstarting material and, oxygen may be raised to the incipient thermalalteration temperature of the starting material through utilization ofthe heat released by the cooling of the 1 product.

In the preferred embodiment of the invention the process is carried outin a continuous regenerative manner by passing a nonfiammable firstmixture containing an exothermically combustible starting material andoxygen through the channels of a first refractory regenerative mass fromthe cooler to the hotter, ends thereof, therebyeflecting incipientthermal alteration of the combustible starting material and producing atflammable second mix ture, passing said second mixture into acombustion and thermal alteration zone wherein the previously initiatedendothermicthermal alteration reaction is propagated by thesimultaneously occurring combustion reaction, thereby producing athirdgaseous mixture hotter than the hottest portions of said firstregenerative mass, and thereafter quenching said third gaseous mixtureby passing the same through the channels of a second regenerative massfrom the hotter to the cooler end thereof, the direction of flow ofgases through said first and second regenerative masses being reversedat suitable intervals whereby a continuous yield of product is obtained.

" The above described continuous regenerative process difiers radicallyfrom the methods of the prior art which entail alternate heatingandpro'duction steps which result in an intermittent flow of desiredproduct. Furthermore, the prior art teaches that the regenerative massesemployed to elfect the thermal cracking of hydrocarbons and the likemust be preheated to a temperature in excess of that required toinitiate cracking, that is, that the regenerative mass must be at leastas hot as the gases produced and that the mass must alone supply theheat requisite not only to initiate but also to propagate theendothermic cracking reaction. Such processes are necessarily attendedby excessive heat loss and therefore of intermittent characteroccasioned by the constantly recurring necessity of reheating theregenerative'mass.

In contrast to such prior art processes, in this invention the productgases when produced are substantially invention is admirably suited byvirtue of its-continuous F nature, both with respect to the introductionof starting materials and to the flow of the product obtained,tooperation under sub-atmospheric or super-atmospheric conditions.Accordingly, the process of the invention is appropriate for theproduction not only of heating gas and unsaturated hydrocarbons frommore saturated starting materials, but also may be employed to advantagein effecting other reactions involving the formation of endothermicreaction products by simultaneous exo thermic combustion and endothermicproduct producing reactions. Thus, sub-atmospheric pressure may appropriately be employed for the production of acetylene, of

3 hydrazine from ammonia, of nitric oxide from air and of other productswhich require extremely rapid quenching to prevent destruction thereof.Such reactions are preferably carried out at a pressure of from about0.2 atmosphere absolute to about 0.8 atmosphere absolute. It will beobvious that both the residence period and the quenching time of thegases in the furnace can be reduced in direct proportion to thereduction in pressure below atmospheric of the gases undergoingtreatment.

Similarly, operation at super-atmospheric pressure is desirably employedfor the production of higher olefins and liquid fuels from highermolecular weight starting materials. Through the utilization of suchsupereatmospheric pressure the longer reaction and quenching periodswhich are of significance in the production of these materials may beachieved.

Certain critical limitations must be observed with respect to thisprocess. It is required that the original mixture contain hydrocarbon orother starting material and oxygen in nonflammable proportions topreclude excessive consumption of the starting material by combustion.Furthermore, only so much oxygen is desirably employed as is required toobtain the heat requisite to the production of the desired pyrolysisproduct. Air, oxygen or oxygen in admixture with gases inert under theconditions may be employed. Air is preferred.

These limits of combustible proportions of the various hydrocarbons andother combustible gases with oxygen are well known to the art. Such datamay be found for example in Handbook of Chemistry and Physics, 30thedition, 1947, p. 1506. The proportions of oxygen or air required toform a combutible mixture with the preferred hydrocarbons for use inthis invention and the preferred proportions for use with these startingmaterials are set forth in Table I, for operations at atmosphericpressure.

1 Parts by volume of oxygen or air per part by volume of hydrocarbon.

It is also essential to the success of the process that both thehydrocarbon or other starting material and the oxygen be preheated tothe incipient cracking or thermal alteration temperature. The additionof unpreheated oxygen or oxygen containing gas to the starting materialraised to the thermal alteration temperature is unsatisfactory.

The hydrocarbon employed may be any hydrocarbon which is gaseous or maybe vaporized under the conditions and which is subject to thermalcracking. Thus low molecular weight compounds such as methane, ethaneand the various isomeric propanes, butanes, hexanes, and mixturesthereof may be employed as Well as higher molecular weight materialssuch as the octanes and decanes and petroleum naphtha. Unsaturatedmaterials may be employed. Low molecular weight, saturated, normallygaseous hydrocarbons such as propane and butane are preferred. However,liquid hydrocarbons may be preheated or atomized and introduced with airto produce good yields of the higher liquid olefins.

The continuous regenerative embodiment of the process of this inventionis attended by a number of unique and outstanding advantages. Aspreviously mentioned, the process may be carried out at high temperaturewithout serious adverse effect upon the refractory of the regenerativemasses utilized for the reason that such masses are always at atemperature substantially lower than the maximum gas temperature.Furthermore, the cracking of hydrocarbons may be effected at extremelyhigh temperatures without the formation of appreciable quantities ofcarbon, thus obviating a serious problem inherent in the processes ofthe prior art. An additional outstanding advantage of the processresides in the fact that the temperature of operation may automaticallybe controlled merely by controlling the composition of the feed mixtureof oxygen containing gas and combustible starting material employed.Furthermore, the process of this invention represents an advance overthe prior art in that there is a remarkably low pressure drop, generallynot more than about 2.5 pounds per square inch therefrom.

It will be apparent that the above described process may be carried outin a plurality of types of apparatus. For example, hydrocarbon andoxygen might be introduced into coils and preheated to incipientcracking temperature, the hot gases mixed and the combined cracking andcombustion permitted to take place in a cracking zone and the hotproducts cooled by passage in heat exchange relationship with theaforementioned preheating coils. This mode of operation is inexpedientin that it entails the use of expensive equipment and temperaturesattained are limited to those possible with alloy metal tubes and coils.

The process of the invention is preferably carried out however in arefractory regenerative furnace structure. It is essential however whensuch a structure is employed at substantially atmospheric pressure thatthe period of residence of the gases undergoing treatment in thatportion of the regenerative mass wherein the gases are heated to thecracking temperature of the starting material not exceed about 0.3second. A preferable range for this residence period is from about 0.05second to about 0.1 second. It is likewise necessary that the period ofresidence of the gases undergoing treatment in that portion of theregenerative furnace wherein the simultaneous combustion and crackingreaction occurs not exceed about 0.05 second. A preferable range forthis period of residence is from about 0.01 second to about 0.03 second.As the product gases are quenched by passage through a secondregenerative mass, the same limits of residence time obtain as thosepreviously defined with respect to the initial heating step.

The foregoing limits with respect to residence time apply to operationsconducted at atmospheric pressure which are suitable for the productionof heating gas, lower olefinic hydrocarbons and the like. When it isdesired to produce acetylene, nitric oxide, hydrazine, hydrocyanicacidand the like, which products require very short residence time in theregenerative masses and extremely rapid quenching, the process of theinvention is elfected at sub-atmospheric pressure. The foregoing limitswill in such cases be reduced to an extent corresponding to thereduction in pressure of operation. For example, if the process iseffected at a pressure of about one-third atmosphere absolute, theresidence time and quenching time can preferably be reduced to below0.01 second. Likewise, when operating at super-atmospheric pressure forthe production of higher liquid olefins, aromatics and the like,correspondingly longer residence periods which favor the reactionsyielding such products are employed. Thus, at a pressure of twoatmospheres residence times as great as about 0.3 second may beemployed. Similarly, when oxygen is utilized in lieu of air, theresidence time in the furnace may be reduced to about one half of thatrequired with analogous operations con ducted with air. Thus, theresidence time when oxygen is utilized may be reduced to a fewthousandths of a second. It will be obvious that the reduction ofresidence and quenching periods by the reduction in pressure in thesystem can be accomplished without appreciable change in pressure dropthrough the regenerative mass because only the lineal gas velocity isincreased, not the mass velocity. This feature of restricted pressuredrop constitutes one of the salient advantages of this invention.

It is also necessary when a refractory regenerative furnace structure isemployed that the pressure drop in the apparatus not exceed about 5pounds per square inch. A preferable range is from about 1 pound persquare inch to about 2.5 pounds per square inch.

The provision of one type of novel regenerative furnace structure inwhich this process may be carried out is one of the salient and primaryfeatures of this invention. Briefly stated, the furnace of the inventioncomprises two regenerative masses having a plurality of uninterruptedflues or slots passing therethrough. Each of said regenerative masses isprovided with a free space at one extremity of the flues for theintroduction or withdrawal of gases. The opposite extremities of theregenerative masses are interconnected with an insulated combustionchamber which is provided with a heating means. of the aforementionedfree spaces is provided with gas admission and withdrawal means whichare in turn associated with means for causing a gas to flow from theaforementioned free space of one regenerative mass through the flues orslots thereof into and through the combustion chamber and thence throughthe fines of the second regenerative mass. Means for the reversing ofthis gas flow are also provided.

This novel furnace structure will now be described in detail withreference to the accompanying drawings in which:

FIGURE 1 represents, partly in vertical section, partly diagrammaticallya complete apparatus in accordance with the present invention, and

FIGURE 2 represents :a horizontal section taken on the line AA of FIGURE1.

In FIGURE 1 there is shown a refractory insulated chamber 1 containingtwo contiguous regenerative checkerworks 2 and 3 both of which areprovided with straight, uninterrupted flues 4. checkerworks 2 and 3 areseparated by gas-tight wall 5 and respectively provided with gas inletand withdrawal spaces 6 and 7, which are in communication with fiues 4.Above the regenerative checkerworks 2'and 3 there is provided aninterconnecting chamber 8 which is in communication with the upperextremities of flues 4 of both regenerative checkerworks 2 and 3.Chamber 8 is provided with heating means 9, normally a burner forgaseous or liquid fuel. Gas inlet and withdrawal lines 10 and 11connected respectively with gas inlet and withdrawal spaces 6 and 7 areconnected through lines 12 and 13 respectively and three way valve 14 toline 15 which in turn leads through valve 16, line 17, valve 18, pump19, and line to a source of hydrocarbon and oxygen containing gas notshown. Valve 18 and pump 19 may be bypassed through line 21, valve 22and line 23. Likewise, gas inlet and withdrawal lines 10 and 11 areconnected through lines 24 and 25 respectively to three way valve 26 andwithdrawal line 27 which in turn leads through valve 28, line 29, valve30, pump 31 and line 32, to storage means not shown. Valve 30 and pump31 may be bypassed by line 33, valve 34 and line 35.

Lines 10 and 1 1 are also connected respectively to lines 36 and 37which function as chimneys during the initial heating of the furnace.Lines 36 and 37 are respectively provided with valves 38 and 39.

Very high heat transfer, short residence period, and low pressure dropin the regenerative furnace are absolutely essential to the successfulpractice of the previously mentioned process for the production of lowdensity heating gas as well as acetylene, other unsaturated hydrocarbonsand other endothermic reaction products. To this end it is necessarythat the above described furnace structure and modifications thereofembraced by this invention conform to certain definite structurallimitations.

It is critical and essential that the length of the regenera Each inlength. Likewise regenerative checkerworks of less,

than about four feet inlength are impractical although the lower limitis not critical. A preferred lengthfor the regenerative checkerworks isfrom about six feet to about ten feet.

It is also essential that the gas passageways or lines 4 in theregenerative checkerwork not exceed about 0.75 inch in maximum width ordiameter. The lower limit of operable width or diameter of such flues isnot necessarily critical but must not be so smallthat excess pressuredrop in the furnace occurs as a consequence thereof. Generally, flues ofmaximum width or diameter of from about 0.75 inch to about 0.25 inch mayfeasibly be employed. Flues of maximum width or diameter of from about0.375 inch to about 0.5 inch are preferred. It will be apparent thatmere masses of promiscuously deposited heat absorbing solids areunsatisfactory regenerative masses for ratio is from about 1:4 to about1:10, and a practical 1 lower limit is about 1:20. This lower limit,however, is not critical except insofar as pressure drop is concerned.

A particularly appropriate type of checker brick for use in theconstruction of the regenerative checkerwork of the furnace of thisinvention is that described and claimed in my co-pending applicationSerial No. 129,969, entitled Regenerative Packing Construction, filedNovember 29, 1949, and now abandoned. 7

These checker bricks are prepared from any conventional refractorymaterial such as the various calcium, magnesium aluminum silicon, iron,chromium, etc. oxides and mixtures thereof. Furthermore, as aconsequence of the thermodynamic advantages of the process of thisinvention in the lower or cooler portions of the regenerative masses, acheckerwork metal such as iron or copper or a checkerwork graphite maybe employed. Preferably the bricks are prepared from a material having ahigh alumina content to obtain maximum heat capacity, highrefractoriness, high thermal stability and inertness toward the gasesundergoing treatment.

The novel placement of the lines or gas passages 4 in this checker brickis diagrammatically shown in FIG- URE 2. It will be observed that all ofthe tines are equidistantly spaced from all the next closest adjoiningflues the lines and interwall thickness are operable within the Ipreviously defined limits with respect to maximum slot size and volume.Conventional checker bricks of other types than those described inaforementioned application preheated. To this end, valves 38 and 39 areopenedand I Ser. 'No. 129,969 may of course be employed if theaforementioned limits are observed.

It is further required that the volume of the combustion chamber 8 notexceed about 60% of the combined volume of the fines 4 in both of theregenerative checkerworks 2 7 and 3. It is preferred that the volume ofthe combos tion chamber 8 be equal to' from about 20% to about I 40% ofthe aforementioned combined volume of the Operation of the furnace andprocess of the invention V i to produce a low density heating gas frompropaneand air will be described by reference to FIGURE 1. Prior toinitiating the cracking reaction the furnace must be valves 16 and 28are closed. Heating means 9 is then actuated in chamber 8 whereby hotcombustion gases are caused to pass downwardly in parallel streamsthrough flues 4 of regenerative checkerworks 2 and 3 into chambers 6 and7 and thence out of the furnace through lines 10 and 36 and 11 and 3.7respectively. During passage through lines 4 the hot combustion gasesproduced by heating means 9 give up heat to regenerative checker-- works2 and 3. The heat transfer efiiciency resultant from the constructionand dimensions of the regenerative checkerworks 2 and 3, previouslydescribed, is such that the combustion gases leave the furnace at atemperature of about 100 C. This procedure is continued until the top ofthe regenerative checkerwork is in excess of 1000 C., preferably withinthe range of 1100 C. to about 1300 C. There is thus provided atemperature gradient in the mass ranging from about 100 C. at thebottomto the temperatures in excess of 1000 C. in the top thereof.

Alternatively, the heating means 9 may be turned off after the top ofregenerative checkerworks 2 and 3 has reached a temperature above theignition temperature of the fuel employed, generally, about 550 to 650C., valves 18, 30, 38 and 39 closed and valves 16, 22, 2% and 34 opened.Combustible material is then introduced through lines and 23, valve 22,lines 21 and 17, valve 16, line 15, valve 14 and lines 13 and 11 to gasinlet '7 from which it passes upwardly through flues 4 of regenerativecheckerwork 3 wherein it is heated to ignition temperature. The heatedcombustible material then passes into combustion space 8 where it burns.The combustion products then pass down through flues 4 of regenerativecheckerwork 2 into gas withdrawal space 6 and thence out of the furnacethrough lines 10 and 24, valve 26, line 27, valve 28, lines 29 and 33,valve 34 and lines 35 and 32. This gas flow is reversed at suitableintervals by reversing three-way valves 14 and 26. The temperatureconditions so obtained in the mass correspond to those previouslydescribed.

This alternative method of heating is particularly advantageous in thata very high flame temperature is obtained in chamber 8 with attendantdecrease in the time required to heat the furnace. Furthermore, the hightemperature zone at the top of regenerative checkerworks 2 and 3 isshorter in length than that resulting from the first described heatingmethod. This result is particularly advantageous when it is desired toproduce a maximum quantity of unsaturated hydrocarbons in a shortresidence time at high temperature.

The operation of the heated furnace to produce low density heating gasby the partial combustion of hydrocarbons is much the same as the lastdescribed heating method. A mixture containing hydrocarbons consistingpredominantly of propane and air in non-combustible proportions of aboutone to two is introduced through lines 20 and 23, valve 22, lines 21 and17, valve 16, line 15, valve 14, and line 11 into gas inlet space 7. Themixture is then passed upward through lines 4 of checkerwork 3. In thecourse of such passage the temperature of the propane is raised untilnear the top of checkerwork sufiicient cracking has occurred to renderthe gas mixture flammable. It will be appreciated that carbon andhydrogen will be formed by the cracking and that the materials will beflammable even with the limited amount of oxygen present. Since there isa deficiency of oxygen, however, only a portion of the combustiblematerials will be consumed. However, only about 15% to about of originalhydrocarbon employed is so dissipated. The balance of the hydrocarbon inthe case under consideration, predominantly propane, is efficientlycracked by the heat released by the aforementioned combustion reaction.The combustion and cracking reactions predominantly occur in combustionchamber 8 where it will be noted the endothermic and exothermic heat aresubstantially equally balanced. It will be obvious that the exothermicheat from the combustion will be absorbed by the endothermic crackingreactions. Furthermore, the sensible heat of 8 the entire gas mixture israised to the flame temperature of the combustion reaction.

By virtue of the type and dimensions of the checkerworks 2 and 3 andchamber 8 of the furnace of this invention, the contact time of thegases in chamber 8 is extremely short, i.e., less than about 0.025second with the result that extremely high yields of unsaturated hydrocarbons are obtained.

Subsequent to the combustion and cracking reaction which predominantlyoccurs in chamber 8, the gas mixture produced passes downwardly throughflues 4 of checkerworks 2 and gives up heat thereto. The mixture thenpasses out through chamber 6, lines 10 and 24, valve 26, line 27, valve28, lines 29 and 33, valve 34 and lines 35 and 32 to storage. Thetemperature of the gas leaving the furnace will be about C.l50 C., whichevidences high thermal efiiciency.

The gas flow through the furnace is continued in the manner specifiedfor approximately one minute and threeway valves 14 and 26 are thensimultaneously reversed. This reversal is preferably accomplished in afraction of a second, in fact so quickly that the continuous flow ofproduct gas passing through valve 26 is not interrupted. The reversal offlow transfers the stream of inlet gas through valve 14, lines 12 and 10and chamber 6 into iiues 4 of checkerwork 2. The gas passes upwardthrough fiues 4, checkerworks 2, is heated to partial cracking, underoes simultaneous cracking and combustion in chamber 8, is quenched incheckerworks 3 and passes out through chamber 7, lines 11 and 25, valve26, line 27 and valve 28, lines 29 and 33, valve 34 and lines 35 and 32to storage. The gas flow is again quickly reversed after operation forone minute and the process so operated continuously. After a period ofsuch continuous operation, the maximum temperature of the regenerativecheckerworks levels off at about 800 C. to 900 C., normally 850 C.

The gas product obtained had the following composition in percent byvolume:

The volume of the product gas as compared with the inlet mixture is1.37. The heating value of the constituents of the product gas per unitvolume is 97% of that of the propane contained in a unit volume of thefeed.

It will be apparent from the foregoing that this invention embraces acontinuous regenerative process for the production of heating gascontaining unsaturated hydrocarbons. This process operates at very highthermal efiiciency by supplying heat internally and by combustion andheat transfer. The exothermic heat is generated by combustion of aportion of the cracked hydrocarbons in a restricted combustion chamberlocated immediately above the checker sections.

The process is completely reversible and establishes a steady statewhich continues indefinitely. It is particularly advantageous in that noreheating, relocation or condensation heating zones in the regenerativemass is required other than that resultant from the simple reversal ofgas flues herein discussed. Furthermore, the absence of rapid andextreme temperature changes greatly prolongs the life of theregenerative checkerwork and thereby eifects substantial economy.

The operation of the furnace in the manner above described results inthe continuous production of low density heating gas containing a highproportion of olefinic hydrocarbons. This mode of operation, whileadmirably suited to the production of such heating gas is not adapted tothe production of acetylene in high yields for the reason that operationunder reduced pressure and more rapid quenching is necessary to preventdecomposition of that product.

Operation at sub-atmospheric pressure may be effected in the apparatusof this invention through utilization of vacuum pump 31. To obtain thebenefits of pump 31, valve 30 is opened and valve 34 is closed. Valve 22or 16 may be throttled to maintain the desired vacuum. The apparatus isotherwise operated in the same manner as that previously described foroperation at atmospheric pressure. A vacuum as great as about 0.2atmosphere absolute may be obtained. Such reduced pressure operatiousare particularly suitable for the production of acetylene, hydrazine andother products which require rapid quenching to prevent decompositionfor the reason that the residence time of the gases undergoing treatmentin the refractory regenerative turnace can be reducedin proportion tothe reduction in pressure below atmospheric. Likewise, yields ofacetylene and the like are increased by the low partial pressure of suchproduct gases in the reaction mixture.

Different ratios of hydrocarbon to oxygen or oxygen containing gas areemployed when it is desired to produce acetylene, than when heating gasis the desired product. Table 11 indicates the preferred ranges in partsby volume of air and oxygen to one volume of methane, ethane, propane,and natural gas for the production of acetylene by operation atsub-atmospheric pressures.

Table II Starting Material Oxygen Air Methane Ethane Prop Natural GasCarbon dioxide Acetylene Carbon monoxide Hydrogen Methane Nitrogen Itwill be observed that the yield of acetylene obtained is more than 60%of theoretical, a higher yield than has heretofore been reported by anycommercial pyrolysis operation. Thus, the novel apparatus and process ofthis invention makes possible a continuous method for the production ofacetylene under reduced pressure and under the optimum conditions ofextremely short residence timc,,i.e., 0.01 second or less, in thereaction zone combined with extremely rapid quenching. Accordingly,there has been developed for the first time a continuous regenerativefurnace operation for the production of acetylene which is operableunder a wide range of pressures and which is attended by no disturbingpressure changes or other adverse effects. An additional result whichhas been achieved by this invention is the production of acetylene inexcellent yield which contains no appreciable contamination of carbonparticles. Hence,the difiiculties of separation of carbon from theproduct acetylene is largely obviated.

It will be appreciated that the method and apparatus of this inventionis equally adapted to continuous operation at super-atmosphericpressures and may be employed to effect endothermic gas reactions whichare favored by such conditions. To achieve this purpose, valve 30 isclosed, valve 34 is opened, valve 22 is closed, and valve 18 is opened.The starting materials are introduced through line 20, in pump 19, theprocess otherwise being conducted in the manner previously described foroperations at atmospheric pressure. Valves 28 and 34 may be throttled tomaintain the desired pressure in the system.

The novel process and regenerative furnace of this invention constitutea significant advance in the art typified by many advantages such asthose hereinbefore described. Obvious modifications of the process andapparatus may be made. Thus, if desired, the furnace might be operatedintermittently. Such a mode of operation however, would dissipate theadvantages of continuous production of product gases which constituteone of the salient features of the invention.

The apparatus of this invention may also be operated by the continuousaddition of a portion of the product to be pyrolyzed through openings inthe heating means 9. As previously pointed out, however, such a mode ofop eration reduces the thermal efilciency of the furnace and negativesthe advantages of the unique structure of the furnace.

This application is a continuation-impart of application Serial No.154,185, filed April 5, 1950, now United States Patent 2,844,452.

Obvious modifications of the apparatus and process of this inventionwill be apparent to those skilled in the art. It will be understood thatthe scope of the invention is restricted only by the sub-joined claims.

What is claimed is:

1. A furnace comprising a heat insulated outer shell, two regenerativemasses having uninterrupted flues therethrough, said regenerative massesbeing positioned in sideby-side relationship, a partition dividing saidregenerative masses, each of said regenerative masses being providedwith a free space in communication with one extremity of said fine, acombustion zone communicating between the extremities of the fiues ofeach of said regenerative masses opposite said free spaces, heatingmeans in association with said combustion zone, means associated witheach of said free spaces for the admission and discharge of a gastherefrom, means associated with said admission and discharge means forforcing a gas into and through the fines of one regenerative mass,through the combustion zone, and then through the gas passageways of theother regenerative mass, and means for reversing the direction of theflow of gas, said regenerative masses being from about four to aboutfifteen feet in length, the maximum cross-sectional dimension of saidflues being from about 0.25 to about 0.75 inch, the ratio of the totalvolume of the fiues in each of said regenerative masses to the totalvolume of the regenerative masses in which said fines are locatedbeingfrom about 1:20 to about 1:3, and the volume of said combustion zonebeing from about 20% to about 60% of the combined total volume of thefiues in both of the regenerative masses.

2. The furnace of claim 1' wherein the maximum crossseotional dimensionof the flues is from about 0.375 to about 0.5 inch.

3. The furnace of claim 1 wherein the ratio of the total volume of theflues to the total volume of the regenerative masses in which the finesare located is from about 1:4-to-about 1:10.

4. The furnace of claim 1 wherein the volume of the regenerative zone isfrom about 20% to about 40% of the combined total volume of the flues inboth of the regenerative masses.

5. The furnace of claim 1 wherein the regenerative masses are from aboutsix to about ten feet long.

6. 'Ilhe furnace of claim 1 wherein the flues in the regenerativernasses are circular in shape and are equidistantly spaced from the nextclosest adjoining flues 1 1 1 2 whereby the thickness of the Wallsbetween adjoining fines References Cited in the file of this patentTendmd umfom- UNITED STATES PATENTS 7. The furnace of claim 1 whereinthe regenerative masses are from about six to about ten feet-long, themaximum cross-sectional dimension of the fines is from 5 2,622,864Hasche about 0.375 to about 0.5 inch, the ratio of the fines to2,692,819 Hasche et a1 26, the total volume of the regenerative massesin which said 23441452 Haschfi July 1958 flues are located is from about1:10 to about 1:4, and the volume of said combustion zone is fironlabout 20% FOREIGN PATENTS to about 40% of the combined total volume ofthe fines 10 583,851 Germany Sept. 13, 1933 in both of the regenerativemasses.

2,491,518 Ribiett Dec. 20, 1949 I

1. A FURNACE COMPRISING A HEAT INSULATED OUTER SHELL, TWO REGENERATIVEMASSES HAVING UNINTERRUPTED FLUES THERETHROUGH, SAID REGENERATIVE MASSESBEING POSITIONED IN SIDEBY-SIDE RELATIONSHIP, A PARTITION DIVIDING SAIDREGENRATIVE MASSES, EACH OF SAID REGENERATIVE MASSES BEING PROVIDED WITHA FREE SPACE IN COMMUNICATION WITH ONE EXTREMITY OF SAID FLUE, ACOMBUSTION ZONE COMMUNICATING BETWEEN THE EXTREMITIES OF THE FLUES OFEACH OF SAID REGENERATIVE MASSES OPPOSITE SAID FREE SPACES, HEATINGMEANS IN ASSOCIATION WITH SAID COMBUSTION ZONE, MEANS ASSOCAITED WITHEACH OF SAID FREE SPACES FOR THE ADMISSION AND DISCHARGE OF A GASTHEREFROM, MEANS ASSOCIATED WITH SAID ADMISSION AND DISCHARGE MEANS FORFORCING A GAS INTO AND THROUGH THE FLUES OF ONE REGENERATIVE MASS,THROUGHT THE COMBUSION ZONE, AND THEN THROUGH THE GAS PASSAGEWAYS OF THEOTHER REGENERATIVE MASS, AND MEANS FOR REVERSING THE DIRECTION OF THEFLOW OF GAS, SAID REGENERATIVE MASSES BEING FROM ABOUT FOUR TO ABOUTFIFTEEN FEET IN LENGHT, THE MAXIMUM CROSS-SECTIONAL DIMENSION OF SAIDFLUES BEING FROM